This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. NLSL.PC is a PC version of non linear least squares program for fitting CW spectra based on microscopically order but macroscopically disorder (MOMD) model. A service request was received from Ms Sarah-Ellen Leonard on the usage of the NLSL.PC program from ACERT website to study the dynamics of a spin labeled protein by multi-frequency ESR spectroscopy.